In recent years, electrochemical cells have been studied actively. Of the electrochemical cells, for example, a fuel cell includes a system for causing electrochemical reaction between a fuel such as hydrogen and an oxidant such as oxygen to generate electric power. Above all, a polymer electrolyte membrane fuel cell (PEFC) applies a light load to the environment and has thus been put into an active use as a household stationary power source or an automotive power source. As a catalyst layer included in each electrode of the PEFC, a carbon-supported catalyst, obtained by supporting a catalyst material on a carbon black support, is in general use. Due to power generation of the fuel cell, the carbon support corrodes to cause great degradation of the carbon layer and a membrane electrode assembly (MEA) including the catalyst layer, and a large amount of catalyst is thus in use for ensuring the durability of the fuel cell. One big challenge for widespread use of PEFCs is to decrease an amount of usage of the noble metal catalyst, so as to reduce cost.
In the fuel cell, for avoiding the degradation of the catalyst caused by the carbon support and enhancing the catalyst activity and the characteristics of the electrochemical cell, a support-less porous catalyst layer has been proposed, and even a small amount of platinum has been able to ensure excellent durability and excellent characteristics.
Meanwhile, since the electrolyte membrane used in the electrochemical cell has been very expensive, the membrane electrode assembly also costs high, which has generally been a big problem in widespread use. Further, for improving the performance of the electrochemical cell, generally, the thickness of the electrolyte membrane has been decreased to reduce the membrane resistance. However, it is known that in the electrolyte membrane sandwiched between the electrodes, large mechanical stress due to swelling and contraction of the electrode ends caused by moisture fluctuations therein is applied to the electrolyte membrane portion outside the electrodes and the electrolyte membrane portion sandwiched between the electrodes, and hence cracking in the membrane and the like easily occur. As described above, the MEA cannot be said to have been developed sufficiently, and needs further improvement.